class Book :
    number = 0
    def __init__(self,name) -> None:
        self.name = name
print(Book.number)
Book.number += 1
print(Book.number)

class Book2 :
    number = 0
    def __init__(self,name) -> None:
        self.name = name
        Book2.number += 1
b1 = Book2("《西游记》")
print(Book2.number)
